// Copyright (C) 2024 EA group inc.
// Author: Jeff.li lijippy@163.com
// All rights reserved.
// This program is free software: you can redistribute it and/or modify
// it under the terms of the GNU Affero General Public License as published
// by the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
//
// This program is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
// GNU Affero General Public License for more details.
//
// You should have received a copy of the GNU Affero General Public License
// along with this program.  If not, see <https://www.gnu.org/licenses/>.
//
//
// This file provides CityHash64() and related functions.
//
// It's probably possible to create even faster hash functions by
// writing a program that systematically explores some of the space of
// possible hash functions, by using SIMD instructions, or by
// compromising on hash quality.

#include <turbo/hash/internal/city.h>

#include <string.h>  // for memcpy and memset
#include <algorithm>

#include <turbo/base/config.h>
#include <turbo/base/endian.h>
#include <turbo/base/internal/unaligned_access.h>
#include <turbo/base/optimization.h>

namespace turbo::hash_internal {

#ifdef TURBO_IS_BIG_ENDIAN
#define uint32_in_expected_order(x) (turbo::gbswap_32(x))
#define uint64_in_expected_order(x) (turbo::gbswap_64(x))
#else
#define uint32_in_expected_order(x) (x)
#define uint64_in_expected_order(x) (x)
#endif

    static uint64_t Fetch64(const char *p) {
        return uint64_in_expected_order(TURBO_INTERNAL_UNALIGNED_LOAD64(p));
    }

    static uint32_t Fetch32(const char *p) {
        return uint32_in_expected_order(TURBO_INTERNAL_UNALIGNED_LOAD32(p));
    }

// Some primes between 2^63 and 2^64 for various uses.
    static const uint64_t k0 = 0xc3a5c85c97cb3127ULL;
    static const uint64_t k1 = 0xb492b66fbe98f273ULL;
    static const uint64_t k2 = 0x9ae16a3b2f90404fULL;

// Magic numbers for 32-bit hashing.  Copied from Murmur3.
    static const uint32_t c1 = 0xcc9e2d51;
    static const uint32_t c2 = 0x1b873593;

// A 32-bit to 32-bit integer hash copied from Murmur3.
    static uint32_t fmix(uint32_t h) {
        h ^= h >> 16;
        h *= 0x85ebca6b;
        h ^= h >> 13;
        h *= 0xc2b2ae35;
        h ^= h >> 16;
        return h;
    }

    static uint32_t Rotate32(uint32_t val, int shift) {
        // Avoid shifting by 32: doing so yields an undefined result.
        return shift == 0 ? val : ((val >> shift) | (val << (32 - shift)));
    }

#undef PERMUTE3
#define PERMUTE3(a, b, c) \
  do {                    \
    std::swap(a, b);      \
    std::swap(a, c);      \
  } while (0)

    static uint32_t Mur(uint32_t a, uint32_t h) {
        // Helper from Murmur3 for combining two 32-bit values.
        a *= c1;
        a = Rotate32(a, 17);
        a *= c2;
        h ^= a;
        h = Rotate32(h, 19);
        return h * 5 + 0xe6546b64;
    }

    static uint32_t Hash32Len13to24(const char *s, size_t len) {
        uint32_t a = Fetch32(s - 4 + (len >> 1));
        uint32_t b = Fetch32(s + 4);
        uint32_t c = Fetch32(s + len - 8);
        uint32_t d = Fetch32(s + (len >> 1));
        uint32_t e = Fetch32(s);
        uint32_t f = Fetch32(s + len - 4);
        uint32_t h = static_cast<uint32_t>(len);

        return fmix(Mur(f, Mur(e, Mur(d, Mur(c, Mur(b, Mur(a, h)))))));
    }

    static uint32_t Hash32Len0to4(const char *s, size_t len) {
        uint32_t b = 0;
        uint32_t c = 9;
        for (size_t i = 0; i < len; i++) {
            signed char v = static_cast<signed char>(s[i]);
            b = b * c1 + static_cast<uint32_t>(v);
            c ^= b;
        }
        return fmix(Mur(b, Mur(static_cast<uint32_t>(len), c)));
    }

    static uint32_t Hash32Len5to12(const char *s, size_t len) {
        uint32_t a = static_cast<uint32_t>(len), b = a * 5, c = 9, d = b;
        a += Fetch32(s);
        b += Fetch32(s + len - 4);
        c += Fetch32(s + ((len >> 1) & 4));
        return fmix(Mur(c, Mur(b, Mur(a, d))));
    }

    uint32_t CityHash32(const char *s, size_t len) {
        if (len <= 24) {
            return len <= 12
                   ? (len <= 4 ? Hash32Len0to4(s, len) : Hash32Len5to12(s, len))
                   : Hash32Len13to24(s, len);
        }

        // len > 24
        uint32_t h = static_cast<uint32_t>(len), g = c1 * h, f = g;

        uint32_t a0 = Rotate32(Fetch32(s + len - 4) * c1, 17) * c2;
        uint32_t a1 = Rotate32(Fetch32(s + len - 8) * c1, 17) * c2;
        uint32_t a2 = Rotate32(Fetch32(s + len - 16) * c1, 17) * c2;
        uint32_t a3 = Rotate32(Fetch32(s + len - 12) * c1, 17) * c2;
        uint32_t a4 = Rotate32(Fetch32(s + len - 20) * c1, 17) * c2;
        h ^= a0;
        h = Rotate32(h, 19);
        h = h * 5 + 0xe6546b64;
        h ^= a2;
        h = Rotate32(h, 19);
        h = h * 5 + 0xe6546b64;
        g ^= a1;
        g = Rotate32(g, 19);
        g = g * 5 + 0xe6546b64;
        g ^= a3;
        g = Rotate32(g, 19);
        g = g * 5 + 0xe6546b64;
        f += a4;
        f = Rotate32(f, 19);
        f = f * 5 + 0xe6546b64;
        size_t iters = (len - 1) / 20;
        do {
            uint32_t b0 = Rotate32(Fetch32(s) * c1, 17) * c2;
            uint32_t b1 = Fetch32(s + 4);
            uint32_t b2 = Rotate32(Fetch32(s + 8) * c1, 17) * c2;
            uint32_t b3 = Rotate32(Fetch32(s + 12) * c1, 17) * c2;
            uint32_t b4 = Fetch32(s + 16);
            h ^= b0;
            h = Rotate32(h, 18);
            h = h * 5 + 0xe6546b64;
            f += b1;
            f = Rotate32(f, 19);
            f = f * c1;
            g += b2;
            g = Rotate32(g, 18);
            g = g * 5 + 0xe6546b64;
            h ^= b3 + b1;
            h = Rotate32(h, 19);
            h = h * 5 + 0xe6546b64;
            g ^= b4;
            g = turbo::gbswap_32(g) * 5;
            h += b4 * 5;
            h = turbo::gbswap_32(h);
            f += b0;
            PERMUTE3(f, h, g);
            s += 20;
        } while (--iters != 0);
        g = Rotate32(g, 11) * c1;
        g = Rotate32(g, 17) * c1;
        f = Rotate32(f, 11) * c1;
        f = Rotate32(f, 17) * c1;
        h = Rotate32(h + g, 19);
        h = h * 5 + 0xe6546b64;
        h = Rotate32(h, 17) * c1;
        h = Rotate32(h + f, 19);
        h = h * 5 + 0xe6546b64;
        h = Rotate32(h, 17) * c1;
        return h;
    }

    // Bitwise right rotate.  Normally this will compile to a single
    // instruction, especially if the shift is a manifest constant.
    static uint64_t Rotate(uint64_t val, int shift) {
        // Avoid shifting by 64: doing so yields an undefined result.
        return shift == 0 ? val : ((val >> shift) | (val << (64 - shift)));
    }

    static uint64_t ShiftMix(uint64_t val) { return val ^ (val >> 47); }

    static uint64_t HashLen16(uint64_t u, uint64_t v, uint64_t mul) {
        // Murmur-inspired hashing.
        uint64_t a = (u ^ v) * mul;
        a ^= (a >> 47);
        uint64_t b = (v ^ a) * mul;
        b ^= (b >> 47);
        b *= mul;
        return b;
    }

    static uint64_t HashLen16(uint64_t u, uint64_t v) {
        const uint64_t kMul = 0x9ddfea08eb382d69ULL;
        return HashLen16(u, v, kMul);
    }

    static uint64_t HashLen0to16(const char *s, size_t len) {
        if (len >= 8) {
            uint64_t mul = k2 + len * 2;
            uint64_t a = Fetch64(s) + k2;
            uint64_t b = Fetch64(s + len - 8);
            uint64_t c = Rotate(b, 37) * mul + a;
            uint64_t d = (Rotate(a, 25) + b) * mul;
            return HashLen16(c, d, mul);
        }
        if (len >= 4) {
            uint64_t mul = k2 + len * 2;
            uint64_t a = Fetch32(s);
            return HashLen16(len + (a << 3), Fetch32(s + len - 4), mul);
        }
        if (len > 0) {
            uint8_t a = static_cast<uint8_t>(s[0]);
            uint8_t b = static_cast<uint8_t>(s[len >> 1]);
            uint8_t c = static_cast<uint8_t>(s[len - 1]);
            uint32_t y = static_cast<uint32_t>(a) + (static_cast<uint32_t>(b) << 8);
            uint32_t z = static_cast<uint32_t>(len) + (static_cast<uint32_t>(c) << 2);
            return ShiftMix(y * k2 ^ z * k0) * k2;
        }
        return k2;
    }

    // This probably works well for 16-byte strings as well, but it may be overkill
    // in that case.
    static uint64_t HashLen17to32(const char *s, size_t len) {
        uint64_t mul = k2 + len * 2;
        uint64_t a = Fetch64(s) * k1;
        uint64_t b = Fetch64(s + 8);
        uint64_t c = Fetch64(s + len - 8) * mul;
        uint64_t d = Fetch64(s + len - 16) * k2;
        return HashLen16(Rotate(a + b, 43) + Rotate(c, 30) + d,
                         a + Rotate(b + k2, 18) + c, mul);
    }

    // Return a 16-byte hash for 48 bytes.  Quick and dirty.
    // Callers do best to use "random-looking" values for a and b.
    static std::pair<uint64_t, uint64_t> WeakHashLen32WithSeeds(
            uint64_t w, uint64_t x, uint64_t y, uint64_t z, uint64_t a, uint64_t b) {
        a += w;
        b = Rotate(b + a + z, 21);
        uint64_t c = a;
        a += x;
        a += y;
        b += Rotate(a, 44);
        return std::make_pair(a + z, b + c);
    }

    // Return a 16-byte hash for s[0] ... s[31], a, and b.  Quick and dirty.
    static std::pair<uint64_t, uint64_t> WeakHashLen32WithSeeds(const char *s,
                                                                uint64_t a,
                                                                uint64_t b) {
        return WeakHashLen32WithSeeds(Fetch64(s), Fetch64(s + 8), Fetch64(s + 16),
                                      Fetch64(s + 24), a, b);
    }

    // Return an 8-byte hash for 33 to 64 bytes.
    static uint64_t HashLen33to64(const char *s, size_t len) {
        uint64_t mul = k2 + len * 2;
        uint64_t a = Fetch64(s) * k2;
        uint64_t b = Fetch64(s + 8);
        uint64_t c = Fetch64(s + len - 24);
        uint64_t d = Fetch64(s + len - 32);
        uint64_t e = Fetch64(s + 16) * k2;
        uint64_t f = Fetch64(s + 24) * 9;
        uint64_t g = Fetch64(s + len - 8);
        uint64_t h = Fetch64(s + len - 16) * mul;
        uint64_t u = Rotate(a + g, 43) + (Rotate(b, 30) + c) * 9;
        uint64_t v = ((a + g) ^ d) + f + 1;
        uint64_t w = turbo::gbswap_64((u + v) * mul) + h;
        uint64_t x = Rotate(e + f, 42) + c;
        uint64_t y = (turbo::gbswap_64((v + w) * mul) + g) * mul;
        uint64_t z = e + f + c;
        a = turbo::gbswap_64((x + z) * mul + y) + b;
        b = ShiftMix((z + a) * mul + d + h) * mul;
        return b + x;
    }

    uint64_t CityHash64(const char *s, size_t len) {
        if (len <= 32) {
            if (len <= 16) {
                return HashLen0to16(s, len);
            } else {
                return HashLen17to32(s, len);
            }
        } else if (len <= 64) {
            return HashLen33to64(s, len);
        }

        // For strings over 64 bytes we hash the end first, and then as we
        // loop we keep 56 bytes of state: v, w, x, y, and z.
        uint64_t x = Fetch64(s + len - 40);
        uint64_t y = Fetch64(s + len - 16) + Fetch64(s + len - 56);
        uint64_t z = HashLen16(Fetch64(s + len - 48) + len, Fetch64(s + len - 24));
        std::pair<uint64_t, uint64_t> v =
                WeakHashLen32WithSeeds(s + len - 64, len, z);
        std::pair<uint64_t, uint64_t> w =
                WeakHashLen32WithSeeds(s + len - 32, y + k1, x);
        x = x * k1 + Fetch64(s);

        // Decrease len to the nearest multiple of 64, and operate on 64-byte chunks.
        len = (len - 1) & ~static_cast<size_t>(63);
        do {
            x = Rotate(x + y + v.first + Fetch64(s + 8), 37) * k1;
            y = Rotate(y + v.second + Fetch64(s + 48), 42) * k1;
            x ^= w.second;
            y += v.first + Fetch64(s + 40);
            z = Rotate(z + w.first, 33) * k1;
            v = WeakHashLen32WithSeeds(s, v.second * k1, x + w.first);
            w = WeakHashLen32WithSeeds(s + 32, z + w.second, y + Fetch64(s + 16));
            std::swap(z, x);
            s += 64;
            len -= 64;
        } while (len != 0);
        return HashLen16(HashLen16(v.first, w.first) + ShiftMix(y) * k1 + z,
                         HashLen16(v.second, w.second) + x);
    }

    uint64_t CityHash64WithSeed(const char *s, size_t len, uint64_t seed) {
        return CityHash64WithSeeds(s, len, k2, seed);
    }

    uint64_t CityHash64WithSeeds(const char *s, size_t len, uint64_t seed0,
                                 uint64_t seed1) {
        return HashLen16(CityHash64(s, len) - seed0, seed1);
    }

}  // namespace turbo::hash_internal
